1. Field of the Invention
The invention relates to a method of increasing the yield of seedlings emerging from seeds in soil and stimulating growth of the seedlings by coating the seeds prior to planting with an aqueous suspension of a water-insoluble alkali lignin. The lignin suspension contains minor amounts of at least one surfactant and the lignin has been ground to a mean particle size of from 0.5 to 5 microns in diameter.
2. Description of the Prior Art
The pelleting, or coating, of seeds was originally designed to produce units of uniform size and shape capable of being drilled singly at any desired distance, thereby eliminating the need for thinning the seedlings. But such pellets have the added advantage of providing seeds with an enlarged bulk, so they can carry in this package whatever chemicals it is desired to apply, both in reasonably large amounts and not in the most intimate contact with the seed itself, thus avoiding possible phytotoxic effects.
U.S. Pat. No. 2,651,883 reports that water-soluble synthetic polyelectrolytes may be used as the resinous binders for coating compositions for seeds. The water-soluble synthetic polyelectrolytes have a substantially continuous carbon chain derived by the polymerization of an aliphatic unsaturated carbon to carbon linkage and have weight average molecular weights in excess of 10,000. The patent also reports an increase in germination of the coated seeds and enhanced growth characteristics of the plant.
U.S. Pat. No. 3,598,565 teaches a coating composition for treating seeds comprising an aqueous emulsion of a substantially water-soluble neutralized copolymer of an .alpha.,.beta.-unsaturated monocarboxylic acid and a lower alkyl acrylate and a crosslinked copolymer of vinyl acetate and a lower alkyl acrylate, which compositions enhance the germination of the coated seeds.
U.S. Pat. No. 3,617,247 teaches seeds coated with carbamylalkenyl phosphorus-containing ester insecticides which act not only in their known insecticidal capacity but enhance the growth of the seedlings and produce an increased ultimate yield of the crop planted.
U.S. Pat. No. 3,674,458 provides a method of regulating the growth of plants involving the treating of seeds with an aqueous solution comprising sodium phenolate, sodium tetraborate, phenol and a humectant, before planting.
There is no known teaching in the prior art of lignin as a seed coating material, although the use of lignin in pesticide formulations as a surfactant or as part of the pesticide delivery system (i.e., as a carrier) is known.
In U.S. Pat. No. 3,726,850, Detroit teaches water-soluble, ozone-oxidized alkali lignin to be pesticide dispersants. U.S. Pat. No. 3,992,532 discloses a method for providing a flowable pesticide formulation with such rheological properties so as to reduce or eliminate sedimentation and liquid phase separation of insoluble pesticides by mixing alkali lignin and liquid toxicant with a hydrocarbon oil and subjecting the mixture to high shear.
U.S. Pat. No. 3,813,236 discloses the chemical covalent bonding of a pesticide to a lignin polymeric substrate. The pesticide is controllably released by destruction of the covalent chemical bonds. U.S. Pat. No. 3,929,453, reissued as Re. No. 29,238, teaches a slow release lignin composite obtained by the coprecipitation-inclusion from an aqueous alkaline lignin solution by adding acid or salts, the drying of a precipitated lignin slurry/pesticide dispersion, or the elimination of a common solvent from a lignin-pesticide mixture.
In other sustained release compositions, U.S. Pat. Nos. 4,184,866, 4,244,728 and 4,244,729, all of which have as a co-inventor the inventor in this application, teach an improved pesticide carrier made by cross-linking an alkali lignin with epichlorohydrin or formaldehyde.
Finally, U.S. Pat. No. 4,381,194, which also has as a co-inventor the inventor in this application, discloses a method for protecting crops from the phytotoxic effect of herbicides and fungicides. The patent teaches combining the herbicide or fungicide with an aqueous suspension concentrate of a water-insoluble alkali lignin containing minor amounts of at least one surfactant wherein the lignin has a mean particle size of from 0.5 to 5 microns in diameter.
Collectively, the prior art relating to agricultural uses of lignin teaches the application of lignin to crops in combination with a pesticide or as a part of a pesticide delivery system. Therefore, the beneficial effects of applying only water-insoluble alkali lignin directly onto seeds resulting in growth stimulation and increased yield of the seedlings was surprising and unexpected.
It is the object of this invention to provide a method of seed treatment wherein seeds are coated prior to planting by contacting the seeds with an aqueous suspension of a water-insoluble alkali lignin, preferably by mixing the seeds in the suspension followed by drying. The alkali lignin suspension contains minor amounts of at least one surfactant and the lignin thereof has a mean particle diameter of from 0.5 to 5 microns.